Production of preserved alkaline paper



United States Patent PRODUCTION OF PRESERVED PAPER 6Claims. (cum-21 This invention relates to paper and is particularly concerned with a method for the manufacture of an alkaline paper which is resistant to the attack of microorganisms.

Papers which are alkaline in reaction exhibit desirable properties which can be adapted advantageously for many uses. For example, problems often arise in the packaging of alkaline materials such as soap with acid reacting paper, wherein a reaction occurs between the alkaline material and said paper at the surfaces of contact. Such problems can be alleviated when alkaline packaging products are employed. Further, papers from kraft fibers developand maintain their greatest mechanical strength under alkaline conditions. This is particularly important in the manufacture of bag stock papers and multiwall paper bags where good mechanical strength is desirable. In addition, the pH of paper or paper products is very important with regard to their resistance to aging. When papers made from a given type of fiber stock are compared, the one which is more alkaline in nature isthe one which shows the greatest degree of permanence.

Papers, however, are oftentimes exposed to conditions which bring about deterioration induced by microorganisms. The preparation of acidic papers which are resistant to microbial attack has been accomplished by incorporating in the paper an antimicrobial agent such as a phenolic compound. In such procedures the antimicrobial phenolic compound is incorporated in the acid reacting, aqueous pulp suspension before the fibers are screened and made into paper according to conventional procedure. Acidic papers made according to such process have retained on their fibers a concentration of phenolic preservative sufficient to impart the property of resisting microorganism induced deterioration. It has been found, however, that when an antimicrobial agent such as pentachlorophenol or its alkali metal salts is incorporated into an alkaline reacting, aqueous pulp suspension and the fibers screened and made into paper according to the conventional procedure, the pentachlorophenol agent is not appreciably retained. by the fibers but is lost in the white Water as a soluble salt. Thus the need for a method of preparing an alkaline paper which is resistant to the attack of microorganisms is well recognized by the paper industries.

According to the present invention it has been discovered that alkaline papers which are resistant to the attack of microorganisms may be prepared from paper pulp suspensions by adding to such suspensions (1) a pentachlorophenol compound, (2) a molar excess with respect to the pentachlorophenol compound of a long chain aliphatic amine compound having at least one hydrogen attached to the amine nitrogen, and (3) 'a paper filler, intimately mixing the resulting modified pulp suspension, diluting the pulp suspension, and thereafter forming a paper web from the modified pulp suspension while the latter is at a pH of from 7.2 to 9.8. In such operation, the pentachlorophenol compound is not entirely dissipated in the white water, but significant residues thereof are in.

2,780,546 Patented Feb. 5, 1957 somemanner and form retained by and associated with the resulting paper and the fibers thereof so as to impart thereto a resistance to attack by microorganisms.

The expression pentachlorophenol compound as herein employed is inclusive of free pentachlorophenol as well as its water soluble salts such as the sodium, potassium and triethanolamine salts, or mixtures thereof.

The expression long chain aliphatic amine compound as used above includes both the free amines, mixtures of such amines, or water soluble salts thereof. Examples of amines which may be used are dodecylamine, decylamine, hexadecylamine, tetradecylamine, octadecenylamine, pentadecylamine, hep'tadecylamine, octadecylamine, dodecyl methylamine, and didodecyl amine, and include the commercially available amines and amine mixtures such as the Armeens of appropriate chain length. Typical of the amine salts which may be employed are hydrochlorides, acetates, formates, tartrates, citrates, phosphates, acid sulfates, hydrobromides and such commercially available salts as the Armacs of appropriate chain length. It is critical and essential that the amine compound be primary or secondary in configuration and contain at least one aliphatic hydrocarbon radical of from 10 to 18 carbon atoms, inclusive.

In practicing the invention, the pentachlorophenol compound is employed in an amount normally adapted to accomplish preservation and in the proportion of at least 0.5 percent by weight based on the weight of the dry pulp. The long chain aliphatic amine compound is incorporated in the mixture preferably in an amount equal to at least 1.5 moles for each mole of employed pentachlorophenol compound. The upper limit of the amine compound is dictated by economic consideration. The range of from about 1.5 to 3 moles per mole of pentachlorophenol compound is considered preferable. Under such conditions of operation, the paper formed retains a sufficient amount of some form of the pentachlorophenol compound to render it resistant to microbial attack.

Good results are obtained when the pentachlorophenol compound is added to the pulp suspension in an amount of 0.5 to 3 percent by weight based on the weight of dry pulp employed in the preparation of the pulp suspension. Thebeneficial results of the present invention are obtained with any of the pulp suspensions employed in paper making in accordance with conventional procedures.

Such suspensions usually contain from 2 to 5 percent by weight of dry pulp. Typical pulp suspensions include those prepared from kraft, soda and sulfite pulp, bleached or unbleached, as well as other chemical and semichemical pulp.

The type of paper filler to be used in accordance with the present teaching is not critical and may be chosen in accordance with conventional practice depending on the particular property desired in the finished paper such as opacity, brightness, smoothness, finish and printability. Any of the alkaline and non-alkaline fillers may be employed and are usually incorporated in the treated pulp suspension in the amount of from about 5 to 10 percent based on the weight of dry pulp. Representative fillers include calcium carbonate, magnesium oxide and titanium dioxide.

Before carrying out the final step of forming a paper web from the treated paper stock it'is critical that the pH of the treated paper stock be in the range 7.2-9.8, inclusive. In general, it will be found that when the amine compound has been added in the form of a free amine or when an alkaline filler has been employed, the resulting paper stock has a pH in the desired range. However, when the amine compound has been added as its salt or when a non-alkaline filler has been used, the

containing 0.2 percent by weight of dry pulp.

the stock solution per sheet.

resultant pulp suspension may have a pH value lower than one in the effective pH range. When such is found to be the case, the pH may be raised by the addition of free amine or alkalineu'eagents such as alkali metal carbonates'or hydroxides. Similarly, apH val'ue higher than 9.8 may be lowered by the addition of'mineral acid, alum or other acidic reagents.

In the successful'practice of this invention, the pentachlorophenol compound, a suitable amine, and a filler are added to an aqueous pulp slurry with sufficient agitation after each addition to insure integration of the additaments, and the resultant slurry "after proper dilution and adjustment of pH ifnecessary is formed into a sheet on a paper machine wire. The order of addition is not critical. Good results may be obtained regardless of whether the pentachlorophenol compound, the amine compound or the filler is'added first and regardless of the sequence followed in the addition of the other two agents. Further, the pentachlorophenol compound and the amine compound may be incorporated by simultaneous as well as by successive addition. If desired, the pentachlorophenol compound and/or amine compounds may be dissolved in water or water-miscible solvent or formed in an emulsion before the addition is made; or the free pentachlorophenol and amine, or salts of pentachlorophenol and amine may be mixed together in a solvent and the solution added to the pulp suspension. It is important, however, that the critical limitations of the amount of pentachlorophenol compound, the amount and kind of amine employed and the pH at which the stock is formed into paper as hereinbefore specified, be observed in the practice of the present invention, if it is desired to obtain alkaline papers containing sufficient of some form of preservative agent to render them resistant to microbial attack.

The following examples illustrate the invention but are not to be construed as limiting:

Example 1 Sodium pentachlorophenolate was added with stirring to a 5 percent aqueous suspension of unbleached sulfite chloride based on the weight of the sodium pentachloroph'enolate. Armeen 12D is a commercially available amine containing 90 percent dodecylamine, 9 percent tetradecylamine and 1 percent octadecenylamine and having a mean molecular weight of 185. An amount of finely powered calcium carbonate filler equal to 10 percent of the dry weight of the paper pulp was then incorporated into the above slurry, and the slurry intimately'mixed and diluted with tap water to give a treated paper stock This treated'paper stock had a pH of 9.0.

Six laboratory handsheets were made with the alkaline stock on a Williams sheet mold using 2500 milliliters of The wet sheets were dried by lightpressing in a Williams hydraulic press, repressing for three minutes at 250 pounds pressure and finally drying at 275 F. for three minutes on a Williams electric drier. Analysis of the finished paper showed a residue of the pentachlorophenol compound in the amount of 0.83 percent by weight of the finished paper, calculated as the sodium salt.

--In this method squares of paper are placed on sterile mineral salt agar in a petri dish and the squares inoculated with the test organism. After incubation for two weeks at 28-30 C., the squares are examined visually to see if any growth has occurred. In such tests the paper sheets were found to completely inhibit the growth of Aspergillus niger, Aspergillus terreus, and Chaetomium globosum.

Example 2 In a further operation, a treated alkaline paper stock was prepared by the same general procedure as described in Example l'except that the calcium carbonate filler was replaced with titanium dioxide, and after'addition of the filler the pH of the slurry was adjusted by'adding a small amount of dilute aqueous alkali. The stock, which had a pH of 8.2, was made into paper sheets in accordance with the aforedescribed method. The sheets were found to contain a residue of thepentachlorophenol compound in the amount of 1.2 percent by weight of the sheet calculated as the sodium salt, and to completely inhibit the growth of the organisms named in Example 1.

Example 3 having "a pH of 8.85. Paper made from this stock according to the method previously described was found to contain a residue of 0.84 percent of the pentachlorophenol compound by weight of the finished sheet calculated as 'thesodium-salt. Tests on the antimicrobial properties showed complete inhibition of growth of the usual test organisms.

Example 4 ha similar'operation, pentachlorophenol and Armeen 12D wereadded-to a 5 percent aqueous unbleached sulfite suspensionas'a mixture of the free phenol and free amine in methanol solvent. The phenol was employed in the amount of 2 percent by weight based upon the weight "of the dry=pulp and the amine in the amount of 200 mole percent based upon the weight of the employed pentachlorophenol. Calcium carbonate filler in an amount of 10 percent by weight was incorporated in the suspension, and the suspension intimately mixed and diluted in the usual fashion to give a stock having a pH of 9.6. When this stock was made into paper as in Example 1, the finished paper contained 0.71 percent residue of the pentachlorophenol compound by weight of the sheet calculated as sodium pentachlorophenolate. The sheets thus prepared completely inhibited the growth of the usual test organisms.

Example 5 Paper stock was prepared by the same general pro cedure as described in Example 1 except that Armac HTD was used in place of Armeen 12D hydrochloride. Armac HTD is a commercially available acetate salt of an amine mixture containing 25 percent hexadecylamine, percent octadecylamine and 5 percent octadecenylamine. The paper stock so prepared had a pH of 9.3. When this stock was made into paper, the sheets were found to have retained a residue of the pentachlorophenol compound in the amount of 0.83 percent by weight calculated as the sodium salt. The paper thus prepared was resistant to microbial attack as evidenced by a complete inhibition of growth of the usual test organisms.

Example 6 Ina further-operation, a methanolic solution of tetra- 'decylamine and sodium pentachlorophenolate are successively added with stirring to a 5 percent aqueous suspension of kraft andsoda pulp. The pentachlorophenolate 5 is employed in the amount of 2 percent by weight based upon the weight of the dry pulp and the amine in the amount of 200 mole percent based upon the Weight of the employed sodium pentachlorophenolate. Stirring is thereafter continued and magnesium oxide filler added to the mixture in the amount of 10 percent by weight of the dry pulp in pulp suspension. The suspension is then adjusted to a pH of 9.0 by the addition of a small amount of alkali and thereafter diluted with water to give a treated paper stock containing 0.2 percent by weight of dry pulp. Paper is made from ,this stock in the manner as previously described and found to contain 0.80 percent of a residue of the pentachlorophenol compound by Weight of the finished sheet calculated as the sodium salt.

We claim:

1. In the process for the manufacture of an alkaline paper from dilute aqueous paper pulp suspension, the steps which comprise adding to the pulp suspension (1) a pentachlorophenol compound in an amount normally adapted to accomplish preservation and (2) a long chain aliphatic amine compound having at least one hydrogen attached to the amine nitrogen and containing from 10 to 18 carbon atoms, inclusive, in the amount of at least 1.5 moles per mole of the added phenolic compound, intimately mixing the resulting modified pulp suspension, and forming the dilute pulp suspension at a pH of from 7.2 to 9.8 into a Waterlaid sheet.

2. In the process for the manufacture of an alkaline paper from paper pulp suspension, the steps which comprise (1) adding to the pulp suspension (a) a pentachlorophenol compound in the amount of from 0.5 to 3 percent by weight of the dry pulp and (b) an amine compound of the group consisting of the primary and secondary aliphatic amines containing at least one aliphatic hydrocarbon radical of from 10 to 18 carbon atoms, inclusive,

and their water soluble salts, in the amount of at least 1.5 moles per mole of the added phenolic compound, (2) diluting the pulp, and (3) thereafter forming a paper web from the modified pulp suspension while the latter is at a pH of from 7.2 to 9.8.

3. A process for the manufacture of an alkaline paper which is resistant to the attack of microorganisms which comprises the steps of 1) adding to a paper pulp suspension (a) a Water soluble pentachlorophenolate in the amount of from 0.5 to 3 percent by weight of the dry pulp, (b) a water soluble salt of a primary aliphatic amine containing from 10 to 18 carbon atoms, inclusive, in the amount of at least 1.5 moles per mole of the added phenolate, and (c) a paper filler, and (2) forming the resulting dilute pulp suspension into a water-laid sheet at a pH of from 7.2 to 9.8.

4. A method claimed in claim 2 wherein the pentachlorophenol compound is sodium pentachlorophenolate.

5. A method claimed in claim 2 wherein the long chain aliphatic amine compound is a primary aliphatic amine hydrochloride containing from 10 to 18 carbon atoms, inclusive.

6. A method claimed in claim 2 wherein the long chain aliphatic amine compound is dodecylamine hydrochloride.

References Cited in the file of this patent UNITED STATES PATENTS 2,161,654 Ellis June 6, 1939 2,182,081 Hatfield Dec. 5, 1939 2,186,134 Chapman Jan. 9, 1940 2,365,833 Morrill Dec, 26, 1944 2,526,892 Minich Oct. 24, 1950 2,668,136 Winkler Feb. 2, 1954 

1. IN THE PROCESS FOR THE MANUFACTURE OF AN ALKALINE PAPER FROM DILUTE AQUEOUS PAPER PULP SUSPENSION, THE STEPS WHICH COMPRISE ADDING TO THE PULP SUSPENSION (1) A PENTACHLOROPHENOL COMPOUND IN AN AMOUNT NORMALLY ADAPTED TO ACCOMPLISH PRESERVATION AND (2) A LONG CHAIN ALIPHATIC AMINE COMPOUND HAVING AT LEAST ONE HYDROGEN ATTACHED TO THE AMINE NITROGEN AND CONTAINING FROM 10 TO 18 CARBON ATOMS, INCLUSIVE, IN THE AMOUNT OF AT LEAST 1.5 MOLES PER MOLE OF THE ADDED PHENOLIC COMPOUND, INTIMATELY MIXING THE RESULTING MODIFIED PULP SUSPENSION, AND FORMING THE DILUTE PULP SUSPENSION AT A PH OF FROM 7.2 TO 9.8 INTO A WATERLAID SHEET. 